Accumulator

ABSTRACT

An object of the present invention is to provide an accumulator including a flow damper which is capable of performing a control so that a vortex may not be formed in a vortex chamber at the time of a large flow injection without requiring huge labors and fabrication costs. The flow damper is configured of a colliding jet controller (a bevel or a projection) for controlling a colliding jet composed of a jet from a large flow pipe and a jet from a small flow pipe flowing into a vortex chamber at the time of a large flow injection so that the colliding jet may proceed directly to an outlet without forming a vortex in the vortex chamber. The colliding jet controller is provided at a junction of an inner surface of the small flow pipe and an inner surface of the vortex chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an accumulator incorporating a flowdamper which is capable of statically switching flow rates from large tosmall. The present invention is useful when applied to an accumulator ofan emergency injection system for a reactor in a pressurized waterreactor (PWR) power plant, for example.

2. Description of the Related Art

An emergency core cooling system is installed in the PWR power plant.The emergency core cooling system includes an accumulator and so forthon the assumption that the PWR might cause a loss of primary coolantaccident.

Water (coolant) is stored in the accumulator, and the water storedtherein is pressurized by a pressurizing gas (nitrogen gas) which isfilled in an upper part in the accumulator. Moreover, a flow damper isprovided in the accumulator. The flow damper can switch a waterinjection flow rate in a reactor from a large flow to a small flowstatically (without moving any part thereof). The flow damper includes avortex chamber, a large flow pipe, a small flow pipe, an outlet pipe andthe like, and is disposed at the bottom in the accumulator (see FIG, 1).A tip end of the outlet pipe is connected to a low temperature pipelineof a reactor primary coolant loop with a check valve interposed inbetween. The check valve is used for avoiding a back flow from a rectorprimary cooling system to the accumulator.

If the pipeline or the like in the reactor primary cooling system of thePWR power plant is broken and the coolant flows out of a crack to theoutside (i.e. upon occurrence of a loss of primary coolant accident),the amount of the coolant in a reactor vessel may be reduced, andthereby a reactor core may become exposed. In this situation, however,if a pressure of the primary cooling system drops below a pressure inthe accumulator, the water stored in the accumulator is injected fromthe primary cooling system pipeline into the reactor vessel through thecheck valve, and thereby refloods the reactor core.

In this case, the reactor vessel is refilled quickly by injecting waterat a large flow rate at an initial stage thereof. Then, it is necessaryto switch the water injection flow rate from the large flow to a smallflow at a later stage when the reactor core is reflooded, becauseexcessively injected water may spill out of the crack. In order toensure this water injection flow rate switching operation, a reliableflow damper without a moving part is used for the accumulator.

The principles of the water injection flow rate switching by use of sucha flow damper will be explained on the basis of FIGS. 10A and 10B(horizontal sectional views).

As shown in FIGS. 10A and 10B, a flow damper 10 has a structure in whicha large flow pipe 2 and a small flow pipe 3 are connected to aperipheral portion (a circumferential portion) of a cylindrical vortexchamber 1, while an outlet 4 is formed in the center of the vortexchamber 1. The large flow pipe 2 and the small flow pipe 3 extend inmutually different directions from the outlet 4. Specifically, the smallflow pipe 3 extends in the left direction along a tangential directionto the peripheral portion (the circumferential portion) of the vortexchamber 1. Meanwhile, the large flow pipe 2 extends in the rightdirection while forming a predetermined angle θ with the small flow pipe3. Moreover, although illustration is omitted, an inlet of the smallflow pipe 3 is located at the same level as the vortex chamber 1.Meanwhile, the large flow pipe 2 is connected to a standpipe whichextends upward. An inlet of this standpipe is located higher than thevortex chamber 1 and the inlet of the small flow pipe 3. Furthermore, anoutlet pipe is connected to the outlet 4 of the vortex chamber 1.

Moreover, since the water level in the accumulator is higher than theinlet of the large flow pipe 2 at the initial stage of water injection,the water in the accumulator flows into the vortex chamber 1 from bothof the large flow pipe 2 and the small flow pipe 3 as indicated witharrows A and B in FIG, 10A. As a result, the injected water (a jet) fromthe large flow pipe 2 collides with the injected water (a jet) from thesmall flow pipe 3, and angular momenta of the jets are offset. In thisway, the water flows directly toward the outlet 4 as indicated with anarrow C in FIG, 10A. Specifically, no vortex is formed in the vortexchamber at this time. Accordingly, a flow resistance is reduced at thistime, and thus a large amount of water flows out of the outlet 4 and isinjected into the reactor vessel.

By contrast, at the later stage of water injection, the water level inthe accumulator drops below the inlet of the standpipe connected to thelarge flow pipe 2. Accordingly, there is no water flow from the largeflow pipe 2 into the vortex chamber 1, and the water flows into thevortex chamber 1 only through the small flow pipe 3 as indicated with anarrow B in FIG, 10B. As a result, the injected water from this smallflow pipe 3 proceeds to the outlet 4 while forming a vortex (a swirlingflow) as indicated with an arrow D in FIG, 10B. Accordingly, the flowresistance is increased by the centrifugal force at this time, and anoutflow (the water injected to the reactor vessel) from the outlet 4becomes a small flow. This device is called a flow damper because it hasthe function to damp the flow rate as described above.

As described above, the accumulator currently in development is theadvanced accumulator which is capable of switching from a large flow toa small flow statically and securely by including the flow damper 10.Moreover, the flow damper 10 of this advanced accumulator is required todefine a proportion between the large flow and the small flow as high aspossible in order to achieve a reasonable tank volume. For this reason,it is essential not to form a vortex in the vortex chamber by surelyoffsetting the angular momenta between the jet from the large flow pipe2 and the jet from the small flow pipe 3 at the time of the large flowinjection. In addition, it is necessary to generate a high flowresistance by forming a strong vortex in the vortex chamber 1 whenswitching from the large flow to the small flow.

For this reason, in the case of a large flow, it is necessary to controlan angle θ defined between the large flow pipe 2 and the small flow pipe3 (a collision angle of the two jets) and the flows (the flow rates) ofthe large flow pipe 2 and the small flow pipe 3 so that the jet from thelarge flow pipe 2 and the jet from the small flow pipe 3 mutually offsetthe angular momenta. Moreover, in the case of a small flow, a strongvortex is formed in the vortex chamber 1 by connecting the small flowpipe 3 to the peripheral portion (the circumferential portion) of thevortex chamber 1 along the tangential direction.

However, in an attempt not to form a vortex in the vortex chamber at thetime of the large flow injection by fine-tuning the values of the angleθ between the large flow pipe 2 and the small flow pipe 3 and the flows(the flow rates) of the large flow pipe 2 and the small flow pipe 3, itis necessary to rebuild the entire flow damper many times in order toadjust these values. Such an attempt may bring about numerous prototypeflow dampers that would involve huge labors and fabrication costs.

SUMMARY OF THE INVENTION

In view of the aforementioned circumstances, it is an object of thepresent invention to provide an accumulator including a flow damperwhich is capable of suppressing formation of a vortex in a vortexchamber at the time of a large flow injection without requiring hugelabors and fabrication costs.

To attain the object, an accumulator according to a first aspect of thepresent invention is an accumulator provided with a flow damper inside,the flow damper including a cylindrical vortex chamber, a small flowpipe connected to a peripheral portion of the vortex chamber along atangential direction thereto, a large flow pipe connected to theperipheral portion while forming a predetermined angle with the smallflow pipe, and an outlet pipe connected to an outlet formed at a centralpart of the vortex chamber. Here, the accumulator is characterized inthat the flow damper includes a colliding jet controller for controllinga colliding jet composed of a jet from the large flow pipe and a jetfrom the small flow pipe flowing into the vortex chamber at the time ofa large flow injection so that the colliding jet may proceed directly tothe outlet without forming a vortex in the vortex chamber, the collidingjet controller being provided at a junction of the small flow pipe andthe vortex chamber.

Moreover, an accumulator according to a second aspect of the presentinvention, in the case of the accumulator of the first aspect, ischaracterized in that the colliding jet controller is a bevel formed atthe junction of the small flow pipe and the vortex chamber.

Furthermore, an accumulator according to a third aspect of the presentinvention, in the case of the accumulator of the first aspect, ischaracterized in that the colliding jet controller is a projectionformed at the junction of the small flow pipe and the vortex chamber.

The accumulator of the first aspect of the present invention ischaracterized in that the flow damper includes a colliding jetcontroller for controlling a colliding jet composed of a jet from thelarge flow pipe and a jet from the small flow pipe flowing into thevortex chamber at the time of a large flow injection so that thecolliding jet may proceed directly to the outlet without forming avortex in the vortex chamber, the colliding jet controller beingprovided at a junction of the small flow pipe and the vortex chamber.Accordingly, it is possible to cause the jet from the large flow pipeand the jet from the small flow pipe to offset the mutual angularmomenta easily and securely so as not to generate a vortex in the vortexchamber at the rime of a large flow only by adjusting a control amountof the colliding jet by use of the colliding jet controller (i.e. onlyby rebuilding the colliding jet controller) instead of rebuilding theentire flow damper. Hence is it possible to drastically reduce laborsand fabrication costs for adjusting the colliding jet.

In particular, according to the accumulator of the second or the thirdaspect of the present invention, either the bevel or the projection isformed as the colliding jet controller, and the colliding jet iscontrolled by use of the bevel or the projection. Hence, it is possibleto obtain a significant effect as similar to the first aspect merely byan extremely simple adjustment work for adjusting either the size of thebevel or a projecting amount of the projection.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention and wherein;

FIG, 1 is a cross-sectional view of an accumulator according to anembodiment of the present invention;

FIG, 2 is an enlarged cross-sectional view extracting and showing a flowdamper included in the accumulator;

FIG, 3 is a plan view of the flow damper;

FIG, 4 is a cross-sectional view taken along, and indicated by, the H-Harrow line in FIG, 2;

FIG, 5A is a cross-sectional view taken along, and indicated by, the I-Iline in FIG, 4, and FIG, 5B is a cross-sectional view taken along, andindicated by, the J-J line in FIG, 4;

FIG, 6 is an enlarged cross-sectional view of a substantial part in FIG,4;

FIG, 7 is a cross-sectional view (a cross-sectional view correspondingto FIG, 4) showing another configuration example of the colliding jetcontroller;

FIG, 8 is an enlarged cross-sectional view (a cross-sectional viewcorresponding to FIG, 6) of a substantial part of the colliding jetcontroller illustrated in FIG, 7;

FIGS. 9A and 9B are views for explaining water injection flow switchingby use of the flow damper; and

FIGS. 10A to 10B are views for explaining water injection flow switchingby use of a conventional flow damper.

FIGS. 11A and 1 lB are cross-sectional views taken along the H-H arrowline in FIG. 2, showing the configuration of curved bevels.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment of the present invention will bedescribed below in detail with reference to the accompanying drawings.

(Configuration)

An accumulator 21 shown in FIG, 1 is an apparatus constituting part ofan emergency core cooling system, which is installed in a pressurizedwater reactor (PWR) power plant on the assumption that a loss of primarycoolant accident might occur in the PWR power plant.

As shown in FIG, 1, water (a coolant) 22 is stored in the accumulator21, and the water 22 stored therein is pressurized by a pressurizing gas(nitrogen gas) 23 which is filled in an upper part in the accumulator21. Moreover, a flow damper 24, which can switch a water injection flowrate in a reactor from a large flow to a small flow statically, isprovided in the accumulator 21.

The flow damper 24 includes a vortex chamber 25, a large flow pipe 26, asmall flow pipe 27, an outlet pipe 28 and the like, and is disposed atthe bottom in the accumulator 21. Although illustration is omitted, atip end of the outlet pipe 28 is connected to a low temperature pipelineof a reactor primary coolant loop with a check valve interposed inbetween. The check valve is used for avoiding a back flow from a rectorprimary cooling system to the accumulator 21.

As shown in FIG, 1 to FIG, 5B, the flow damper 24 has a structure inwhich the large flow pipe 26 and the small flow pipe 27 are connected toa peripheral portion (a circumferential portion) of the cylindricalvortex chamber 25, while an outlet 29 is formed in the center of anupper surface 25 b of the vortex chamber 25. Alternatively, the outlet29 may be provided in the center of a lower surface 25 c of the vortexchamber 25.

In view of horizontal surfaces as illustrated in FIG, 3 and FIG, 4, thelarge flow pipe 26 and the small flow pipe 27 extend in mutuallydifferent directions from the outlet 29. Specifically, the small flowpipe 27 extends in a direction (which is the left direction in thedrawings) along a tangential direction to the peripheral portion (thecircumferential portion) of the vortex chamber 25. Meanwhile, the largeflow pipe 26 extends in another direction (which is the right directionin the drawings) while forming a predetermined angle θ (in a range from90°<θ<180°; such as 95°, 100° or 110°) with the small flow pipe 27.

Cross sections of flow passages of the large flow pipe 26 and the smallflow pipe 27 are formed into rectangular shapes. Specifically, as shownin FIGS. 5A and 5 b, for example, the large flow pipe 26 (a horizontalportion 26 a) has a parallel pair of inner surfaces (vertical surfaces)26 d and 26 e which face each other in the horizontal direction, and aparallel pair of inner surfaces (horizontal surfaces) 26 f and 26 gwhich face each other in the vertical direction. Meanwhile, the smallflow pipe 27 has a parallel pair of inner surfaces (vertical surfaces)27 b and 27 e which face each other in the horizontal direction, and aparallel pair of inner surfaces (horizontal surfaces) 27 d and 27 ewhich face each other in the vertical direction. The heights of theflow-passage cross sections of the large flow pipe 26 and the small flowpipe 27 (the heights of the inner surfaces 26 d and 26 e and of theinner surfaces 27 b and 27 c) are the same as the height of an innerperipheral surface 25 a of the vortex chamber 25. On the other hand, thewidths of the flow-passage cross sections of the large flow pipe 26 (thewidths of the inner surfaces 26 f and 26 g) are greater than the widthsof the flow-passage cross sections of the small flow pipe 27 (the widthsof the inner surfaces 27 d and 27 e).

Moreover, an inlet 27 a of the small flow pipe 27 is located at the sameheight as that of the inner peripheral surface 25 a of the vortexchamber 25. On the other hand, the large flow pipe 26 includes astandpipe 26 b connected to the horizontal portion 26 a, and an inlet 26c thereof is located higher than the vortex chamber 25 and the inlet 27a of the small flow pipe 27. It is to be noted, however, that a waterlevel 22 a of the stored water 22 is usually located higher than thisinlet 26 c of the large flow pipe 26. The outlet pipe 28 is connected tothe outlet 29 of the vortex chamber 25. Anti-vortex plates 30 and 31 arerespectively provided to the inlets 26 c and 27 a of the large flow pipe26 and the small flow pipe 27.

As shown in FIG, 4 and FIG, 6, the inner surface 27 b, at the side ofthe large flow pipe 26, of the small flow pipe 27 is connected to theinner surface 26 e, at the side of the small flow pipe 27, of the largeflow pipe 26. Moreover, in consideration of a spread of a jet from thesmall flow pipe 27 (a free-jet-spread proportion), a junction 32 of theinner surface 26 d, at the opposite side of the small flow pipe 27, ofthe large flow pipe 26 and an extended surface portion (a flat surfaceportion) 25 a-1 of the inner peripheral surface 25 a of the vortexchamber 25 is located outside an extension line of the inner surface 27b, at the side of the large flow pipe 26, of the small flow pipe 27 (theline extending from the junction 33 in the tangential direction). It isto be noted, however, that the present invention is not limited to theforegoing configuration. It is also serves the purpose to adopt astructure in which the junction of the inner surface 26 d and the innerperipheral surface 25 a does not include the extended surface portion(the flat surface portion) 25 a-1 as indicated with a dashed line K inthe drawing.

Moreover, the inner surface 27 c, at the opposite side of the large flowpipe 26, of the small flow pipe 27 is connected to the inner peripheralsurface 25 a of the vortex chamber 25 at a junction 34. This junction 34is located upstream of the junction 33 in terms of the direction of theflow (the direction of the jet: see an arrow B) from the small flow pipe27.

Moreover, in this embodiment, as shown in FIG, 4 and FIG, 6, the flowdamper 24 includes a bevel 41 functioning as a colliding jet controllerwhich is provided at the junction 34 of the small flow pipe 27 (theinner surface 27 c) and the vortex chamber 25 (the inner peripheralsurface 25 a). Specifically, by forming the bevel 41 in an appropriatesize at the junction 34, it is possible to control a colliding jetcomposed of a jet from the large flow pipe 26 and a jet from the smallflow pipe 27 flowing into the vortex chamber 25 at the time of a largeflow injection so that the colliding jet may proceed directly to theoutlet 29 securely without forming a vortex in the vortex chamber 25.

For example, a decrease in the size of the bevel 41 as indicated with adashed line L in FIG, 6 causes an increase in the amount of the jet fromthe large flow pipe 26, which flows along the direction of the jet fromthe small flow pipe 27 while bypassing the bevel 41 as indicated with anarrow N. As a result, the colliding jet composed of the jet from thelarge flow pipe 26 and the jet from the small flow pipe 27 tends to forma clockwise vortex as indicated with an arrow P. On the other hand, anincrease in the size of the bevel 41 as indicated with a dashed line Min FIG, 6 causes a decrease in the amount of the jet from the large flowpipe 26, which flows along the direction of the jet from the small flowpipe 27 while bypassing the bevel 41. As a result, the colliding jetcomposed of the jet from the large flow pipe 26 and the jet from thesmall flow pipe 27 tends to form a counterclockwise vortex as indicatedwith an arrow O.

In other words, it is possible to control the colliding jet by the sizeof the bevel 41. Accordingly, it is possible to cause the colliding jetto proceed directly toward the outlet 29 as indicated with an arrow C byadjusting the bevel 41 into an appropriate size.

Incidentally, the bevel formed at the junction 34 is not limited to thebevel 41 which is cut away in an orthogonal direction to the directionof the jet from the small flow pipe 27 (the tangential direction). Forexample, the bevel may be formed in an oblique direction relative to thedirection of the jet from the small flow pipe 27. Moreover, the bevelmay be a bent bevel or a curved bevel.

Furthermore, the flow damper 24 shown in FIG, 7 and FIG, 8 includes aprojection 51 functioning as the colliding jet controller which isprovided at the junction 34 of the small flow pipe 27 (the inner surface27 c) and the vortex chamber 25 (the inner peripheral surface 25 a). Theprojection 51 in the illustrated example has a plate shape. By formingthe projection 51 in an appropriate projecting amount at the junction34, it is possible to control the colliding jet composed of the jet fromthe large flow pipe 26 and the jet from the small flow pipe 27 flowinginto the vortex chamber 25 at the time of a large flow injection so thatthe colliding jet may proceed directly to the outlet 29 securely withoutforming a vortex in the vortex chamber 25.

For example, an increase in the projecting amount of the projection 51causes an increase in the amount of the jet from the large flow pipe 26,which flows along the direction of the jet from the small flow pipe 27while bypassing the projection 51 as indicated with an arrow Q. As aresult, the colliding jet composed of the jet from the large flow pipe26 and the jet from the small flow pipe 27 tends to form a clockwisevortex as indicated with the arrow P. On the other hand, a decrease inthe projecting amount of the projection 51 causes a decrease in theamount of the jet from the large flow pipe 26, which flows along thedirection of the jet from the small flow pipe 27 while bypassing theprojection 51. As a result, the colliding jet composed of the jet fromthe large flow pipe 26 and the jet from the small flow pipe 27 tends toform a counterclockwise vortex as indicated with the arrow O.

In other words, it is possible to control the colliding jet by theprojecting amount of the projection 51. Accordingly, it is possible tocause the colliding jet to proceed directly toward the outlet 29 asindicated with the arrow C by adjusting the projecting amount of theprojection 51 into an appropriate size.

Incidentally, the projection formed at the junction 34 is not limited tothe projection 51 which is projected straight in the direction of thejet from the small flow pipe 27 (the tangential direction). For example,the projection may be formed into a plate in an oblique directionrelative to the direction of the jet. Moreover, the projection may be abent projection or a curved projection. Furthermore, the projection maybe formed into a shape other than the plate shape (one having atriangular horizontal cross section is also applicable, for example).

(Operation and effects)

The accumulator 21 having the above-described configuration exerts thefollowing operation and effects.

If a pipeline or the like in a reactor primary cooling system of a PWRpower plant is broken, and the coolant flows out of a crack to theoutside (i.e. upon occurrence of a loss of primary coolant accident),thereby reducing a pressure of the primary cooling system below apressure in the accumulator 21, the stored water 22 in the accumulator21 is injected from the primary cooling system pipeline into a reactorvessel through a check valve, and thereby refloods a reactor core. Atthis time, the water injection flow rate to the reactor vessel isswitched from a large flow to a small flow statically by way of the flowdamper 24.

Specifically, since the water level in the accumulator 21 is higher thanthe inlet 26 c of the large flow pipe 26 at an initial stage of waterinjection, the water 22 in the accumulator 21 flows into the vortexchamber 25 from both of the large flow pipe 26 and the small flow pipe27 as indicated with arrows A and B in FIG, 9A. As a result, theinjected water (a jet) from the large flow pipe 26 collides with theinjected water (a jet) from the small flow pipe 27, and angular momentaof the jets are offset. In this way, the water 22 flows directly towardthe outlet 29 as indicated with an arrow C in FIG, 9A. Specifically, novortex is formed in the vortex chamber 25 at this time. Accordingly, aflow resistance is reduced at this time, and a large amount of waterflows out of the outlet 29 and is injected into the reactor vessel.

By contrast, at a later stage of water injection, the water level in theaccumulator 21 drops below the inlet 26 c of the standpipe connected tothe large flow pipe 26. Accordingly, there is no water 22 flowing fromthe large flow pipe 26 into the vortex chamber 25, and the water 22flows into the vortex chamber 25 only through the small flow pipe 27 asindicated with an arrow B in FIG, 9B. As a result, the injected waterfrom this small flow pipe 27 proceeds to the outlet 29 while forming avortex (a swirling flow) as indicated with an arrow D in FIG, 7B.Accordingly, the flow resistance is increased by the centrifugal forceat this time, and an outflow (the water injected to the reactor vessel)from the outlet 29 becomes a small flow. Although FIG, 9 illustrates theexample of providing the bevel 41, similar water injection flow rateswitching is achieved in the case of providing the projection 51 aswell.

Moreover, according to the accumulator 21 of this embodiment, the flowdamper 24 includes the colliding jet controller (the bevel 41 or theprojection 51), which is configured to control the colliding jetcomposed of the jet from the large flow pipe 26 and the jet from thesmall flow pipe 27 flowing into the vortex chamber 25 at the time of alarge flow injection so that the colliding jet may proceed directly tothe outlet 29 without forming a vortex in the vortex chamber 25, thecolliding jet controller being provided at the junction 34 of the smallflow pipe 27 and the vortex chamber 25. Accordingly, it is possible tocause the jet from the large flow pipe 26 and the jet from the smallflow pipe 27 to offset the mutual angular momenta easily and securely soas not to generate a vortex in the vortex chamber 25 at the rime of alarge flow, only by adjusting a control amount of the colliding jet byuse of the colliding jet controller (i.e., only by rebuilding thecolliding jet controller in the vortex chamber 25) instead of rebuildingthe entire flow damper 24. Hence is it possible to drastically reducelabors and fabrication costs for adjusting the colliding jet.

In particular, according to the flow damper 24 of this accumulator 21,either the bevel 41 or the projection 51 is formed as the colliding jetcontroller, and the colliding jet is controlled by use of the bevel 41or the projection 51. Hence, it is possible to obtain a significanteffect as described above merely by an extremely simple adjustment workfor adjusting either the size of the bevel 41 or the projecting amountof the projection 51. Incidentally, application of the bevel or theprojection for controlling the colliding jet may be selected asappropriate depending on the angle θ between the large flow pipe 26 andthe small flow pipe 27 or on the proportion of the flows (the flowrates) between the large flow pipe 26 and the small flow pipe 27 (i.e. abalance in the angular momenta between the jet from the large flow pipe26 and the jet from the small flow pipe 27), for example.

The invention thus described, it will be obvious that the same way maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. An accumulator provided with a flow damper inside, the flow damperincluding a cylindrical vortex chamber, a small flow pipe connected to aperipheral portion of the vortex chamber along a tangential directionthereto, a large flow pipe connected to the peripheral portion whileforming a predetermined angle with this small flow pipe, and an outletpipe connected to an outlet formed at a central part of the vortexchamber, wherein the flow damper comprises a colliding jet controllerfor controlling a colliding jet composed of a jet from the large flowpipe and a jet from the small flow pipe flowing into the vortex chamberat the time of a large flow injection so that the colliding jet mayproceed directly to the outlet without forming a vortex in the vortexchamber, the colliding jet controller is a bevel formed at a junction ofthe small flow pipe and the vortex chamber, and said bevel is formed ina predetermined shape having a predetermined surface, in which saidpredetermined surface extends from an inner surface, which is located atthe opposite side of the large flow pipe, of the small flow pipe to aninner peripheral surface of the vortex chamber.
 2. The accumulatoraccording to claim 1, wherein the bevel formed at the junction being inan oblique direction relative to the direction of the jet from the smallflow pipe.
 3. The accumulator according to claim 1, wherein the bevelformed at the junction being bent.